The production of putative osteoclasts in tissue culture - ultrastructure, formation and behavior.

A system for culture of cat bone marrow produces multinucleate cells (50-100 nuclei) of large proportions (300 micrometer diameter). Scanning and transmission electron microscopy indicates that these cells (not virally induced syncytia) are true osteoclasts, which exhibit ultrastructural aspects of bone resorption (ruffled border and clear zones in TEM section, active spatulate cytoplasmic extensions in the SEM) even after 6 weeks culture on a plastic substratum. Observations have also been made regarding the formation of the multinucleate cells from apparently specific mononuclear precursors, and the behaviour of these cells on various substrata is also reported.